The crystal structural evolution of nano-Si anode caused by lithium insertion and extraction at room temperature

The crystal structure and morphology of nanosized Si particles and wires af ter Li-insertion/extraction electrochemically have been studied by ex-situ XRD, Raman spectroscopy and electronic microscopy. It is confirmed that the insertion of lithium ions at room temperature destroys the crystal structu re of Si gradually and leads to the formation of metastable amorphous Li-Si alloy, Furthermore, local ordered structure of Si can be restored after th e partial extraction of lithium ions, which indicates the extraction of lit hium ions promoting the recrystallization of amorphous Li-inserted Si. It w as also observed that nanosized Si particles and wires were merged together after the insertion/extraction of lithium ions. (C) 2000 Elsevier Science B.V. All rights reserved.